Commonly, the fabrication of color filters for liquid crystal displays involves the coating of resist liquid onto a substrate, which includes a sheet of glass, in order to provide triple-layers of red (R), green (G) and blue (B) or to provide a protective surface layer or geometric shapes. For high precision coating required for the fabrication, spin coating has been used. In spin coating, an excessive amount of resist material, which is costly, is applied onto the surface of a substrate, and the substrate is rotated at a high speed. The spin coating poses the problem that the radial velocity of the rotating substrate causes a substantial portion of the resist material to be scattered away from the substrate surface, thereby wasting a large amount of the applied resist material and causing high production costs.
This problem of spin coating makes it desirable to improve coating processes by using a coating die head such that the spin coating is no longer needed.
However, the known coating processes of this kind fail to accomplish desired thickness uniformity of a coating layer because they allow occurrence of stripes extending in a direction of the movement of a substrate and steps lying laterally with respect to the direction of the movement of the substrate.